1. Field of the Invention
This invention relates to polymer bound light stabilizers, to curable compositions and to curing processes employing such curable compositions for providing same, more particularly this invention provides cured or partially cured epoxy resins containing bound light stabilizing groups. Still more particularly this invention provides light stabilized epoxy resins which are the product of the reaction of
A) some of the epoxy groups of an epoxy resin composition an average of 1.75 or more epoxide groups per molecule with
B) a hydrazido functionalized hindered amine light stabilizer of Formula I or II or combinations thereof and optionally a hydrazido functionalized 2-(2-hydroxyphenyl)-2H-benzotriazole of Formula III wherein x and the various R groups are as defined hereinafter, and optionally an auxiliary epoxy curing agent. ##STR1##
2. Description of the Prior Art
Dihydrazides of carboxylic acids are well known curing agents for epoxy resins. For example see
Encyclopedia of Polymer Science and Technology, John Wiley & Sons, Inc., Vol. 6 235 (1967). PA1 U.S. Pat. Nos.: 2,847,395; 3,014,009; 3,102,043; 3,876,606; 4,377,680; 4,585,698. PA1 U.S. Pat. Nos. 4,544,733; 4,530,991; 4,448,949, 4,450,267; 4,337,680. PA1 E. P. 154,455. PA1 J. P. 85 168,717. PA1 JP 84 109,519; JP 84 113,022; JP 84 164,321; JP 79 04,944 and Fr. Demande FR 2,517,304.
Numerous patents have recently issued covering structurally different hydrazides as latent curing agents for epoxy resins.
Kamon and Saito [T. Ramon and K. Saito, Kobunski Ronbunshu 37 (12), 765-771 (1980)]determined the curing mechanism for the reaction of aliphatic dihydrazides with epoxy resins was the reaction of the epoxy group with the active hydrogen atoms on the terminal nitrogen atoms of the dihydrazide similar to the reaction of epoxy resins with diamines. The resins cured smoothly when heated above 150.degree. C.
Other examples of using dihydrazides as curing agents include:
U.S. Pat. No. 3,530,173 and East German Patent DD 155,324 (CA 97,183414k) teach the use of cyanocarboxylic acid hydrazide to cure epoxy resin.
However none of the hydrazide compounds described in these references contain light stabilizing groups attached to them. Russian investigators have prepared macromolecular phenolic antioxidants by treating epoxy group-containing butadiene-isoprene copolymer with 3-(2,6-di-t-butyl-4-hydroxyphenyl)propionhydrazide at 150.degree. C. for 6 hours in an inert atmosphere. (N. S. Domnina, E. V. Kornilova, V. S. Shagov, Vestn. Lennigr. Univ., Ser. 4: Fiz. Khim. 1988, (3), 69-73 (Russ); C.A. 110 (21): 174861 m.
U.S. Pat. No. 4,855,084 teaches the inclusion of anthraquinone compounds containing hydrazide substituents into epoxy resin compositions. The resulting compositions are photosensitive and can be reduced by UV light. They are especially useful in the production of printed circuits.
U.S. Patent Application Ser. No. 275,452 filed Nov. 23, 1988, now U.S. Pat. No. 4,927,891 discloses the attachment of hindered amine light stabilizers containing a hydrazide functionality and hydrazido functionalized 2-(2-hydroxyphenyl)-2H-benzotriazole to acrylic coating resins by reacting them with glycidyl methacrylate segments in the acrylate copolymer. No concrete evidence was presented to demonstrate whether the hydrazide group attacked the epoxy functionality or the ester functionality to become attached to the coating resin. The coatings showed excellent UV stability.
U.S. Patent Application Ser. No. 455,219 filed Dec. 22, 1989 now abandoned discloses the reaction of N-HALS Amic Acid Hydrazides of Formula I with mono glycidyl ethers.
It is well known in the literature to attach light stabilizers to epoxy resins by reacting hydroxy, carboxy, thio or amino-functionalized light stabilizers with resins containing two or more terminal vicinal epoxides. This is normally done to increase the molecular weight of the stabilizer and thereby make it less volatile, less extractable and in many cases more compatible with host polymer systems to be stabilized.
In U.S. Pat. Nos. 4,797,436 and 4,771,091, oligomeric tetraalkylpiperidine light stabilizers were prepared by reacting known polyalkyldiazospirodecanes with epoxides. The products were used to stabilize polymers against the damaging effect of light, heat and oxygen.
U.S. Pat. No. 4,371,644 discloses the reaction of the hindered nitrogen of various 2,2,6,6-tetraalkylpiperidines with epoxides to form 1-substituted 2,2,6,6-tetraalkylpiperidines which have superior stabilizing activity against photo and thermal degradation and are less volatile and less extractable.
U.S. Pat. No. 4,480,084 teaches chain extending polyalkylpiperidines on the hindered nitrogen with an excess of epoxy resin to form a diepoxide functional polymer which is then capped with hydroxy functional monomer to provide a crosslinkable polymeric hindered amine light stabilizer particularly suitable for use in coating compositions.
British Patent 1,574,999 and European Patent 003,542 also teach the preparation of polymeric light stabilizers by reacting the hindered nitrogen of various polyalkylpiperidines with various epoxy resins.
British Patent 1,568,725 teaches the use of 4-amino-2,2,6,6-tetramethylpiperidine as a curing agent for epoxy resins. Epoxy resin films hardened with 4-amino-2,2,6,6-tetramethylpiperidine showed surprisingly good UV stability for epoxy resins.
U.S. Pat. No. 4,469,829 teaches the attachment of 4-amino-2,2,6,6-tetramethylpiperidine to 1,3-polybutadiene containing epoxy groups to obtain polymer bound hindered amine light stabilizers.
Japanese Patent JP 85 168 729 teaches the preparation of polymer bound UV absorbers by reacting epoxy resins and 4-amino benzoic acid. (CA 104 34970x).
U.S. Pat. No. 4,292,195 teaches the preparation of non-fugitive antioxidants by reacting secondary aromatic amines containing a pendant amino group with a polyepoxide. The reaction products are particularly useful as antioxidants for rubbers and plastics especially if the rubbers or plastics are subject to solvents which normally would extract a significant portion of conventional antioxidants.
J. Luston et. al. (J. Luston and Z. Manasek, J. Appl. Polymr. Sci., Vol. 21, 915-922 (1977) prepared non-volatile UV absorbers by reacting epoxy resins with 2,4-dihydroxy-5-t-butylbenzophenone. The product was claimed to be useful in polypropylene fibers which are spun at 330.degree. C.
U.S. Pat. No. 4,801,660 teaches the curing of epoxy resins with mercaptan-containing polyphenols. The compositions are particularly useful as adhesives and have good moisture resistance.
Ger. Offen 2,916,877 (EP 019,103) teaches the attachment of hindered phenol antioxidants containing carboxylic acid groups to glycidyl ethers and esters and cycloaliphatic epoxides and triglycidyl isocyanurate (Ca 94 85143m) to make migration resistant stabilizers for polyolefins.
U.S. Pat. No. 4,585,693 teaches the attachment of UV absorbers containing reactive functionality such as amine, hydroxyl or carboxylic acid groups to acrylateglycidyl methacrylate copolymers by reaction with the pendant glycidyl group.
U.S. Pat. No. 4,544,691 teaches the modification of UV absorbers (oxanilides, benzalmalonates, .alpha.-cyanocinnamates and o-hydroxyphenylbenzotriazoles) containing phenolic hydroxyl groups with alkyl glycidyl ethers. The modified UV absorbers are less volatile, more compatible in coating formulations and have free hydroxyl groups that are capable of binding chemically with the coating components of acrylic and polyester enamels that are crosslinked with hydroxymethyl melamine and/or alkoxymethyl melamine curing agents.
U.S. Patent Application Ser. No. 310,425 filed Feb. 13, 1989, now U.S. Pat. No. 4,981,914 teaches the attachment of hydrazide functionalized benzotriazoles to polymers containing at least one ester, epoxide, or anhydride functional group in the polymer backbone, on grafted side chains or as a pendant unit.
In conclusion, the prior art teaches the curing of epoxy resins with carboxylic acid hydrazides and dihydrazides. It also teaches that it is advantageous to attach hindered amine light stabilizers and UV absorbers to epoxy resins and epoxides. The modified stabilizers are less volatile, more compatible with host polymers and less extractable with solvents. There are no references to my knowledge of attaching hydrazido functionalized hindered amine light stabilizers (or UV absorbers) to epoxy resins (exclusive of the acrylate/glycidyl methacrylate copolymers of U.S. Patent Application Ser. No. 275,452 filed Nov. 23, 1988 now U.S. Pat. No. 4,927,891) by reaction of the hydrazide group with the epoxy (glycidyl ether) group of the resin.